1. Technical Field
The present invention relates to a machine for detecting a sheet-like object with high degrees of reliability and accuracy of validation for the sheet-like object, and a validating machine using it.
2. Related Background Art
There are a wide variety of conventionally known validating machine for scanning both sides of a sheet-like object to optically detect compositions of the both sides of the object. Many of the validating machine of this type are generally classified under reflective validating machine and transmissive validating machine. For example, Patent Document 1(Japanese Patent No. 2896288) describes a bill validating method applicable to the reflective validating machine for detecting an optical characteristic of reflected light from an object (bill) to validate the object. This bill validating method is specifically as follows. This method is to preliminarily detect characteristics of reflected light from sample objects (real bills) and register a detected signal pattern thereof (hereinafter referred to as a reference pattern). In an actual validation process, reflected light from a bill is detected as the bill is illuminated with light from a light emitting device, and a detected signal pattern thereof is compared with the reference pattern to validate the authenticity of the bill.
For example, Patent Document 2(Japanese Patent Application Laid-Open No. 2003-77026) describes a transmissive validating machine for detecting an optical characteristic of transmitted light from an object (bill) to validate the object. This transmissive validating machine specifically validates the authenticity of the bill as follows. This transmissive validating machine preliminarily detects characteristics of transmitted light by sample objects (real bills) and registers a detected signal pattern thereof (hereinafter referred to as a reference pattern).
In an actual validation process, the machine detects transmitted light through a bill as the bill is illuminated with light from a light emitting device, and compares a detected signal pattern thereof with the reference pattern to validate the authenticity of the bill.
Incidentally, bill forging techniques have quickly advanced in recent years, and it is the case that forged bills similar to real bills can be made accurately and easily. Since designs of front and back sides of such forged bills are extremely similar to those of real bills, the optical characteristics of light (reflected light and transmitted light) from the front and back sides are also much the same as those of real bills. This means that the detected signal pattern of reflected light or transmitted light from a forged bill virtually conforms to the reference pattern.
Therefore, the validation using reflected light or transmitted light as in the aforementioned validating method and validating machine in Patent Documents 1 and 2 could bring about the possibility of validating a forged bill extremely close to a real bill, as a real bill, thus posing a problem of lack of reliability and accuracy of validation to check the authenticity.